Railsconf 2010

Scaling Rails on App Engine
with JRuby and Duby
Run your apps on Google Servers,
with access to first-class Java APIs
John Woodell
David Masover
Ryan Brown
June 9, 2010

2

Friday, June 11, 2010

Google App Engine
3


Key Features
• No need to install or maintain your own stack
• Use Google scalable services via standard APIs
• Built-in application management console
• Pay-as-you-go, with free quota to get started

4


Key Limitations
• No native code
• No threads or sockets
• No writing to the filesystem
• No more than 30 seconds per request

5


Quotas and Billing
Resource Provided Free Additional Cost
CPU time 6.5 hours/day $0.10/hour

Bandwidth In 1GByte/day $0.10/GByte

Bandwidth Out 1GByte/day $0.12/GByte

Stored Data 1 GB $0.005/GB-day

Emails sent 2000/day to users $0.0001/email
50000/day to admins

6


App Engine Product Roadmap
• SSL for third-party domains
• Background servers capable of running for longer than 30s
• Ability to reserve instances to reduce application loading overhead
• Ability to select different availability vs. latency options for Datastore
• Support for mapping operations across datasets
• Datastore dump and restore facility
• Raise request/response size limits for some APIs
• Improved monitoring and alerting of application serving
• Support for Browser Push (Comet) communication
• Built-in support for OAuth & OpenID

7


JRuby on App Engine
8


Benefits of JRuby
• Outperforms MRI in many cases... 2x to 10x
• Gem extensions written in Java (no more segfaults)
• A wealth of integration options and first-class Java APIs

9


App Engine JRuby Milestones
• 2009-04-08 @olabini publishes blog post on YARBL
• 2009-04-09 @nicksieger publishes warbler demo
• 2009-05-06 RailsConf (sinatra & merb)
• 2009-11-02 0.0.5 bundler, precompilation & Duby preview
• 2009-11-20 RubyConf (Rails 3.0.pre & Duby App)
• 2009-12-27 @urekat publishes Rails 2.3.5 patches
• 2010-01-11 @codingforrent published rails/dm gem
• 2010-01-21 0.0.8 Rails 2.3.5 Primer for DM & TinyDS
• 2010-01-26 0.0.9 Mechanize and Hpricot demos
• 2010-02-27 0.0.10 ActionMailer, ImageService, jruby-openssl
• 2010-04-08 @azazeal blog post on taxster.gr (OpenID)
• 2010-06-09 0.0.14 JRuby 1.5.1 & app.yaml preview
10


Current Issues with JRuby on App Engine
• Several seconds to “spin-up” a new JRuby instance
• Some gems may need their extensions ported to Java
• Not officially supported , but you have all that you need

+
11


Install it Now

sudo gem install google-appengine

Everything you need installs as gems

12


App Engine Gems
• Development Gems
– appengine-sdk
– appengine-tools . . . dev_appserver.rb & appcfg.rb
• Runtime Gems
– appengine-rack . . . . jruby-jars & jruby-rack
– appengine-apis
• Related Gems
– dm-appengine
– rails_appengine
– rails_dm_datastore
– rails_tiny_ds

13


App Engine JRuby APIs
• AppEngine::Users
• AppEngine::Datastore
• AppEngine::Memcache
• AppEngine::Mail
• AppEngine::URLFetch
• AppEngine::Images
• AppEngine::Logger
• AppEngine::XMPP
• AppEngine::Labs::TaskQueue
• AppEngine::OAuth
• AppEngine::Blobstore

14


dm-appengine
David Masover

15


DataMapper

16


ActiveRecord contains SQL strings

17


Use AppEngineResource

18


Relationships

19


Simple

20


Transactions
• Idempotence
– "Why can't I click submit more than once?"
• Transactions on datastore
– Optimistic locking
– Atomic
– Only across entity-groups

21


Simple case is Simple

22


Entity-groups

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Global transactions
• Don't do them!
• Really, you don't need them!
• They wouldn't scale anyway!
but sometimes...

24


Inventory tracking

25


Shopping Cart

26


Duby
Ryan Brown


Duby’s not Ruby
• Statically typed
• No Duby runtime
• Uses Java’s type system

28


Duby has Ruby-inspired Syntax

def fib(a:int)
if a < 2
a
else
fib(a - 1) + fib(a - 2)
end
end

puts fib 10


// Generated from examples/Test.duby

public class Test extends java.lang.Object {

public static void main(String[] argv) {
System.out.println(Test.fib(10));
}

public static int fib(int a) {
return (a < 2) ?
(a) :
((Test.fib((a - 1)) + Test.fib((a - 2))));
}

}


A Simple Duby App
import javax.servlet.http.HttpServlet
import com.google.appengine.ext.duby.db.Model

class Post < Model
property title, String
property body, Text
end

class DubyApp < HttpServlet
def_edb(list, 'com/ribrdb/list.dhtml')

def doGet(request, response)
@posts = Post.all.run
response.getWriter.write(list)
end

def doPost(request, response)
post = Post.new
post.title = request.getParameter('title')
post.body = Text.new(request.getParameter('body'))
post.save
doGet(request, response)
end
end

31


A Simple Duby App

class Post < Model
property body, Text
end Types
class DubyApp < HttpServlet inferred from parent
class
end

post = Post.new
post.save
end
end

32


A Simple Duby App

class Post < Model
property body, Text
end
Plugins
class DubyApp < HttpServlet

end

post = Post.new
post.save
end
end

33


Duby Supports Plugins
Only form of metaprogramming (for now)

require 'erb'

Duby::AST.defmacro('def_edb') do |duby, fcall, p|
name = fcall.args_node.get(0).name
path = fcall.args_node.get(1).value
erb = ERB::Compiler.new(nil)
...
src = erb.compile(IO.read(path))
duby.eval(src, p, “(edb)”)
end


Duby Can Use erb Templates
<title>Posts</title>
<body>
<h1>All Posts:</h1>
<% for post in @posts %>
<h2><%= post.title %></h2>
<p><%= post.body.getValue %></p>
<% end %>
<hr>
<h1>New Post:</h1>
<form method=post>
Title: <input type=text name=title><br>
Body: <textarea name=body></textarea><br>
<input type=submit>
</form>
</body>


More to Come
• Open classes
• Mix ins
• Macros
• More

36


Resources
• Blog
– http://jruby-appengine.blogspot.com/
• Code Site
– http://code.google.com/p/appengine-jruby/
• Google Group
– http://groups.google.com/group/appengine-jruby

• Resources
– http://rails2010-dm.appspot.com/
– http://github.com/masover/rails2010
– http://github.com/masover/cart
– http://cart-demo.appspot.com/

37


Railsconf 2010

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